Date of Award

8-2007

Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Chemical Engineering

Advisor

Douglas W. Bousfield

Second Committee Member

Joseph M. Genco

Third Committee Member

Vincent Caccese

Abstract

When paper is printed in the heatset web offset printing process, waviness is sometimes observed in the final product. These waves align themselves in the machine direction and resemble sine waves with wavelengths ranging from 5 to 20 mm, and amplitudes in few hundred microns. This printing defect is often called "fluting". Although this problem has been around for sometime, litde work has been done to understand the cause for this waviness. A number of theories have been proposed but none seem to explain all of the industrial findings. A novel technique was developed to characterize fluting which uses a laser light source in conjugation with MathCAD. Laser light when focused at low angles takes the shape of the object placed in its path. The image of the object is then captured by a camera and analyzed. The program in MathCAD reads each pixel from top to bottom of the image and picks the edge of bright or red colored pixel and records the point on the graph, a number of such points put together gives the shape of the edge traced by laser light. The edge is again converted back into cross section profile of the sample in desired units by calibrating scale. The technique developed was used to study the effect of different parameters like moisture and tension in a base sheet for light weight coated grade, super calendered (SC) paper and a wood free paper. The effect of changing the moisture content at constant tension, it was found that all the three samples behaved similarly but the number of waves per unit cross section was less in the case of base sheets of wood free sample when compared to super calendered and light weight sample. When tension was changed keeping the moisture content constant it was observed that base sheets of super calendered and light weight papers behaved similarly but wood free paper appeared to have higher wavelengths and more cockled than fluted. The effect of web length, printed area and type of drying (fast and slow) was studied in base sheet for a light weight coated grade. Increasing the web length decreased amplitudes but wavelengths were not affected. Printed area and type of drying had no significant effect on both amplitudes and wavelengths of fluting. A coating was prepared which was applied on to base sheet of light weight sample using rod. Amplitudes and wavelengths of coated sheets were higher than in the base sheets when moisture content was changed at constant tension. In case of varying tension at constant moisture content amplitude data was observed to be scattered in both base sheet and coated sheet but wavelengths of base sheets were higher than coated sheets.

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